Dust formation during the course of mining operations has been a long-standing problem in the industry. With the advent of modern high-speed cutting and pulverizing equipment, those problems associated with dust formation have increased. The problems are particularly acute in long wall mining of coal where shears chop one length of wall up to 1500 feet in length in one continuous operation.
Among the problems are inhalation of dust particles by mining personnel, fire and explosion, machine tool wear from particle invasion of moving parts, etc. Avoidance of these and other problems have led to the advent of numerous devices for providing maximum ventilation, spraying the air with water in the general vicinity of the cutting operations, and even vacuuming or aspirating the air immediately surrounding cutting operations.
Irrespective of health and maintenance problems, governmental regulation also must be satisfied. Standard have been and continue to be promulgated which define acceptable mine dust levels.
Water spray is one popular control techniques because it is generally efficient and economical. Known water spray techniques are employed to reduce the quantity of dust at the work site thereby minimizing the above-mentioned health danger to workers as well as equipment fouling problems caused by the dust. One key point for water spray application is that it is most efficient when the spray is concentrated directly at the cutting site.
Examples of devices employed for this purpose are found in U.S. Pat. No. 4,358,160 describing a long wall shear or mining machine with a series of water-spray nozzles fixed along the upper surface of the mining device and on a static arm extending along the backside of the main body of the machine. One of the static arms depicted not only serves to support the nozzles but also serves as the support for a passive curtain barrier. In operation, the nozzles spray water in a direction behind the machine with the intention of generating a quasivertical laminar air flow to contain the dust created during the mining operation from the operator.
Another device, illustrated in U.S. Pat. No. 4,488,759, is directed to controlled fluid spray application at a work site such as a coal seam whereby dust generated by the impacting of the tool is entrained within and by the fluid spray.
One additional consideration for construction and maintenance of fluid spray devices is protection. During long wall mining operations, large rocks or sections of coal may fall onto the top of the shearing machine and can damage fixed position, stable components of that machine. It has been known that falling debris, when large enough, will develop sufficient force to cause serious damage by snapping components from the machine.